Over the past few years, a wealth of new data has become available on the structure of the ribosome. Of particular importance are the crystal structures of several ribosomal proteins and cryoelectron microscopic images with a resolution of about 15[unreadable]. The new data have validated some aspects of earlier models for the structure of the ribosome, but they have also revealed a number of problems with those models. The quality and quantity of these data offer opportunities for the development of better and more accurate models of the ribosome. In addition, the improved methods that we have developed -- particularly the generation of starting models for YAMMP refinement using distance geometry, and the addition of new descriptions of proteins, transfer RNA, and messenger RNA -- will enable us to generate the next generation of ribosome models much more rapidly and with fewer problems than in the past. We have evaluated all the available data, established a suitable set of constraints from the data, and generated preliminary models using the combined distance geometry / YAMMP refinement approach. We expect to complete these second generation efforts during the next year of the grant.